Light-field imaging is the capture of four-dimensional light-field data that provides not only spatial information regarding light received from a scene, but also angular information indicative of the angle of incidence of light received from the scene by the camera's optical elements. Such four-dimensional information may be used to project a variety of two-dimensional images, including images at various focus depths, relative to the camera. Further, the light-field information may be used to ascertain the depth of objects in the scene. Yet further, the light-field information may be used to enable and/or facilitate various image processing steps by which the light-field and/or projected two-dimensional images may be modified to suit user requirements.
In conventional photography, a wide variety of autofocus systems are used. In phase detection autofocus implementations, the camera typically has a separate optical pathway, which may be accessed by diverting some of the incoming light away from the path leading to the image sensor used to capture the image. The diverted light may be conveyed to an autofocus module, which may include several pairs of miniature image sensors. Each pair may be positioned to measure the focus at a particular focus point in the scene. Such autofocus systems can add significantly to the cost, expense, and complexity of the camera, and can cause the loss of some of the light that could otherwise be used to facilitate proper image exposure in the main image sensor.
Contrast detection autofocus systems may determine the level of focus of image data by assessing the contrast of the image. Such systems may not require the use of a separate optical pathway for implementation of the autofocus system; however, such systems may require the lens to sweep through a broad range of focus positions, capturing images at each one, so that the contrast levels of the images can be compared. Thus, contrast detection autofocus systems may be relatively slow in operation.
Accordingly, known autofocus systems for conventional and light-field image capture are deficient in many respects. Phase detection and contrast detection autofocus systems both have significant drawbacks that have not been sufficiently addressed.